The objective of this proposed project is to continue our study of the visual accommodation system. Our study to date has led us to consider three important aspects: voluntary control, involuntary control, and interaction with eye movements. We have shown that voluntary control of accommodation is very easily trained. This has interesting applications and has clarified the care needed in conducting experiments aimed at determining the nature of accommodative control mechanisms. Subjects readily learn to utilize even subtle cues that offer information on the polarity or magnitude of focus change. We also suspect that there is an involuntary control system that may involve only the central part of the fovea. A basic problem in automatic focus control is determination of the polarity of focus. (First-order blur is nominally the same on either side of best focus.) We have developed a model which suggests that the familiar lag in visual accommodation may be functional in biasing accommodation away from optimum focus, as a result of which proper polarity information is then available. A primary interest of this project is trying to prove the existence of this involuntary system and to determine its operational characteristics. We have developed two novel instruments: a high-speed, automatic, infrared optometer and a two-dimensional eye tracker, which has an accuracy of the order of one minute of arc. To conduct our proposed studies it is necessary to combine these two operational instruments so that they can operate simultaneously on the same eye. This is necessary both for being able to stabilize an image on the retina, in order to search out this central foveal region, and to explore the interaction of the eye movement and accommodation systems. Merging a sensitive optometer and highly accurate eye tracker into a single composite instrument would have important uses apart from our own immediate applications.